streetzlegend

iTrader: (2)

I just did a compression test, just for the hell of it, and to see if i had a very low cylinder causing my misfire but thats not the issue.

So facing the engine here are my results:

200 , 197 , 200
175 , 170 , 170

So I am wondering why the front bank is lower than the rear, although I think its within reasonable compression, at least within stock compression.

I then looked at the manifold and found that that the runners going to the front have a bronze'ish color (perhaps normal oil mist from the turbo or from previous motor coating the manifold with oil from pcv), So I am thinking that the methanol/water is making its way to the runners for the rear easier than to the front, hence why the runners for the rear looks cleaner. For now I am going to lay off the meth (sounds funny lol).

Any opinions, suggestions?

streetzlegend

iTrader: (2)

Word...

GT-ER

iTrader: (4)

I'm guessing you have a FWD VQ.

Anyways you have a variation of 30psi from the weakest cylinder to the strongest cylinder...that's more than twice the tolerance my G35 FSM allows. You might have damaged ringlands which could cause the problem.

ashtrojan2008

iTrader: (1)

my compression has never been that high. but gt-er is right, 30psi is a huge difference from cylinder to cylinder. I'd just keep an eye on it. Re check compression and do a leakdown after a few more k miles. My cylinder 3 is a little low (10psi from the others) so i'm gonna keep an eye on it.

ross

ashtrojan2008

iTrader: (1)

also was the engine warm when you checked compression? that can make a big difference

BonesZ33

iTrader: (2)

Big difference. Make sure battery is fully charged also

streetzlegend

iTrader: (2)

Yeah, I didnt drive the car around before doing the test but I let it idle to operating temp's then turn it off, took manifold off and did the test. Battery eventually died after I did the second round, i did test twice to get the average. For the rear ones which are the high ones, the needle would stop at 180 then a couple of more cranks and it would jump to 200's. Next time I do the test, im going to actually drive the car, and make sure oil and everything is warm.

Just frustrating because I cant come up with any reason why I would have broken ring or ringlands. I havent heared a single knock on this motor since day one, and my J&S has been doing its job if there ever was a time it needed to retard timing. I have no oil consumption or anything, just the regular blowby smoke from crank case which is vented to atmosphere. Also no smoke out the tail when WOT or ever. Only issue I have is misfire in boost.

ashtrojan2008

iTrader: (1)

i wouldnt worry about it too much, i think your engine is fine. you'd have some oil consumption/smoke if there was a major problem. Just try get it thoroughly warm and on a hot battery and try again. let us know if you find anything else.

and as far as the misfire, that still an issue? i wouldn't boost it much until that is resolved.. good luck!

also, what is your compression ratio? head gasket thickness? just curious.

ross

streetzlegend

iTrader: (2)

Thanks man, yeah the misfire is still there. Took off the meth, returned, lowered the timing, still missing. Car pulls hard as heck but still missing, im just going to relax and drive it like a normal daily driver for a while, and figure out the misfire one day. Its my only car.

twitch579

iTrader: (3)

Does it log a misfire code? Did u try the dumb stuff like plugs and coils? I would try find out which exact one is misfiring.

streetzlegend

iTrader: (2)

Yup, got new coils, also increase the voltage to them, plugs are rather new. They dont have any sign of issues either, detonation, melting, nothing.

GT-ER

iTrader: (4)

I'd honestly not worry about it since it pulls hard and hasn't exploded yet. This is usually a good sign...lol.

Misfires are usually too much fuel ( check wideband ), too little fuel ( again, wideband ), bad spark plugs ( change them out ), bad plug gap ( check gap ), bad ignition coil.

Usually in the order I put it.

streetzlegend

iTrader: (2)

Wideband shows 11's afr. gap is .029, was at .026 before and still missed. Coils are getting 15v via an amp I have on there so the spark is strong. Plugs dont look like they are in bad shape at all, might just change them for the hell of it.